(a) Field of the Invention
This invention relates to a method for determining the amount of copolymerized vinyl monomer in a copolymer formed by copolymerizing acrylonitrile and a vinyl monomer. Acrylonitrile copolymers of this type which contain from 0 to 25% by weight of the vinyl monomer are referred to hereinafter as "acrylonitrile/vinyl monomer copolymers" or simply "A/V copolymers".
(b) Description of the Prior Art
Acrylic textile fibers prepared from A/V copolymers are widely used to provide apparel and homefurnishing fabrics. The dyeing properties of these acrylic fibers are dependent on the level of copolymerized vinyl monomer in the fiber, that is, variations in the level of copolymerized vinyl monomer in the fiber leads to variations in the annealing shrinkage of the fiber which in turn causes variations in the rate at which basic dye will diffuse into the fiber. Accordingly, to achieve fabrics having good dye uniformity characteristics the level of copolymerized vinyl monomer in the fibers from which the fabrics are constructed must be controlled within a narrow range which in turn requires a good analytical method for measuring the level of copolymerized vinyl monomer in the fiber or the copolymer from which the fiber is formed.
Present analytical methods (e.g., infrared methods) used to measure the level of copolymerized vinyl monomer in A/V copolymers involve rather complicated procedures and provide only a mediocre degree of accuracy. Accordingly, there is a need in the art to provide a simple method by which the level of copolymerized vinyl monomer can be more accurately measured, thereby enabling fibers and fabrics of improved dye uniformity to be obtained. The main object of the present invention is to provide such a method.